Several national and multi-national vehicle safety organizations have formulated pedestrian safety standards which new vehicles are measured against. At least one such safety standard utilizes a test procedure which simulates a vehicle striking the upper leg of a pedestrian standing or walking in front of the vehicle. For some vehicle designs, contact with the upper leg is made by the leading edge of the vehicle hood and/or portions of the vehicle immediately below the hood leading edge.
Some motor vehicles have a front-end shape that is relatively low for visibility, aerodynamic, and/or styling reasons. As a result, there may be a relatively small amount of clearance between the front-end panels (hood, fender, grille, head lamps, etc.) and the vehicle's structural frame and/or other rigid components (powertrain, suspension, etc.) beneath the panels (within the engine bay, for example). In general, more clearance is believed to improve pedestrian safety because it provides “crush space” through which the relatively deformable front-end panels can deflect when struck by a pedestrian. Exterior panel deformation absorbs kinetic energy of the collision before the pedestrian strikes the rigid components inside the vehicle front-end.
It has been proposed to increase the under-hood crush space by raising or lifting the vehicle hood from its normal operating position immediately prior to a pedestrian impact. Known systems include crash detection and/or prediction sensors that trigger actuators which adjust the position of the hood in reaction to the detected/predicted impact. Raising the vehicle hood, however, may not provide sufficient reduction in severity of injury caused by the leading edge of the hood striking the pedestrian's upper leg.
U.S. Pat. No. 7,845,691B2 discloses a pedestrian safety system in which a pedestrian collision sensing device activates a hood release and a lifting actuator to raise the hood to a raised condition, thereby providing additional deformation space beneath the hood.